.pic {
    width: 100%;
    height: 310px;
    background: url(../images/合作.webp) no-repeat center;
    background-size: cover;
    position: relative;
}

.pic span {
    text-align: center;
    font-family: "MTTiJ", "PingFang SC", "Microsoft YaHei UI", "Microsoft YaHei", "Source Han Sans CN";
    font-size: 52px;
    color: rgb(255, 255, 255);
    position: absolute;
    top: 41%;
    left: 31%;
}

/* .content {
    margin: 60px 40px;
    position: relative;
    display: flex
} */

/* .left1 {
    width: 200px;
    /* background-color: lightgrey; */
/* float: left; 
    margin-right: 30px;
    position: sticky;
    top: 0;
    left: 51px;
} */

/* .right2 {
    width: 1100px;
    /* background-color: orange; */
/* float: left; 
    position: relative;
    top: 0;
    /* left: 235px; */
/* padding-left: 200px; 
    width: 100%;
} */

.content {
    margin: 60px 40px;
    position: relative;
    /* 仅作为位置参考 */
}

.left1 {
    width: 200px;
    position: fixed;
    /* 关键：相对于浏览器窗口固定 */
    /* 基于.content的margin计算位置，确保在content范围内 */
    top: 445px;
    /* 等于.content的margin-top */
    left: 91px;
    /* .content的margin-left(40px) + 51px */
    margin-right: 30px;
}

.right2 {
    width: 1100px;
    margin-left: 235px;
    /* 给左侧导航留空间 */
}

.left1 ul li {
    display: block;
    width: 180px;
    height: 40px;
    line-height: 40px;
    padding-left: 53px;
    color: rgb(17, 25, 37);
    cursor: pointer;
    font-family: "PingFang SC", "Microsoft YaHei UI", "Microsoft YaHei";
    font-size: 14px;
    position: relative;
    /* 关键：让伪元素相对于li定位 */
}

.left1 ul::before {
    content: '';
    background-color: rgba(17, 25, 37, .06);
    border-radius: 4px;
    bottom: 12px;
    display: block;
    left: 27px;
    position: absolute;
    top: 11px;
    width: 6px;
    height: 180px;
}

/* 黄色指示点 - 默认隐藏 */
.left1 li::before {
    content: '';
    position: absolute;
    left: 27px;
    top: 43%;
    width: 6px;
    height: 24px;
    /* border-radius: 50%; */
    background: rgb(242, 242, 112);
    transform: translateY(-50%);
    opacity: 0;
    transition: opacity 0.3s;
}

/* 选中状态显示黄色指示点 */
.left1 li.active::before {
    opacity: 1;
}

footer {
    clear: both;
}

.right2 h2 {
    font-family: "PingFang SC", "Microsoft YaHei UI", "Microsoft YaHei", "Source Han Sans CN", sans-serif, "Helvetica Neue", Helvetica, Arial;
    font-size: 28px;
    color: rgb(17, 25, 37);
    padding-left: 20px;
    font-weight: 500;
    margin-bottom: 40px;
    margin-top: 0;
}

.box2 {
    width: 352px;
    height: 140px;
    background-color: #ffffff;
    margin-bottom: 20px;
    /* line-height: 140px; */
    display: inline-block;
    margin-right: 5px;
    border-radius: 8px;
}

.right2 ul {
    margin-left: 20px;
    margin-bottom: 60px;
}

.box2 span {
    display: block;
    font-size: 18px;
    font-weight: bold;
    color: #2c3e50;
    margin-bottom: 4px;
}

.box2 small:first-child {
    display: block;
    color: #7f8c8d;
    margin: 0;
    /* 关键：重置默认margin */
    padding: 2px 0;
}

.right2 ul li:hover {
    background-color: yellow;
    cursor: pointer;
}

.hidden1 {
    display: none;
}
.hidden2 {
    display: block;
} 

.right2 ul li:hover .hidden1 {
    display: block;
}
.right2 ul li:hover .hidden2 {
    display: none;
}

